Expanding projectiles or bullets as known in the art have several advantages over bullets which are not designed to promote expansion, such as “full metal jacket” or “round nose” bullets. For example, when an expanding bullet travels through a target, it can expand, transferring its kinetic energy to the target. Since an expanding bullet can transfer more of its kinetic energy to the target than can a round-nose bullet, an expanding bullet is less likely to exit the target and cause undesired damage. Accordingly, expanding bullets are useful in military, law enforcement, and hunting applications.
Hollow-point bullets are expanding bullets that contain a cavity or “hollow-point” at the front of the bullet. Upon striking a target, the hollow point fills with material from the target, in effect creating a “wedge” or “penetrater” out of the target material. As the hollow-point bullet travels through the target, the target material is forcefully driven into the hollow point, expanding the front of the bullet. In this manner, a hollow-point bullet with sufficient kinetic energy can expand well beyond its original diameter. Further, the loss of kinetic energy due to expansion slows the velocity of the hollow-point bullet, making it less likely that it will exit the target and cause unintentional damage. At a sufficiently high velocity a hollow-point bullet may break into two or more pieces, or fragment, while it is traveling through the target, transferring a large portion of its kinetic energy to the target while further reducing the likelihood of unintentional harm.
Hollow-point bullets have several drawbacks. If bullet velocity is not optimal, then the front of the bullet may only slightly expand, or not expand at all. Hollow-point bullets often fail to expand when the hollow point becomes clogged with certain types of target material, such as heavy clothing. Often, the forward part of a hollow point may expand slightly and then be sheared off, leaving a large cylindrical projectile to travel through and exit the target, transferring minimal kinetic energy to the target and increasing the likelihood of unintentional harm.
To promote bullet expansion, some projectiles utilize a wedge-like solid “ballistic tip” or “penetrater” at the front end of the bullet. Upon striking a target, the penetrater is driven into the bullet, causing the front of the bullet to expand. At sufficiently high velocities the penetrater of a ballistic-tip bullet may be driven far enough within the bullet to cause fragmentation, reducing the chance for unintentional harm. However, if bullet velocity is not optimal, then the front of the bullet may only slightly expand, or not expand at all. Often, the forward part of a ballistic-tip bullet may expand slightly and then be sheared off, leaving a large cylindrical projectile to travel through and exit the target, transferring minimal kinetic energy to the target and increasing the probability of unintentional harm. Under actual shooting conditions, bullet velocity at the target is often not high enough to cause adequate expansion.
Some projectiles in the art use a cylindrical fluid-filled cavity to exert a radial expanding force. Fluid-filled bullets offer several advantages over hollow-point and ballistic-tip bullets. First, there is no hollow point to clog or malfunction as in a hollow-point bullet. Second, fluid-filled bullets can expand more rapidly than either hollow-point or ballistic-tip bullets. Fluid-filled bullets can offer greater expansion at a given velocity than either a hollow-point or a ballistic-tip bullet.
U.S. Pat. No. 5,349,907 to Petrovich discloses a projectile having a cylindrical cavity containing a fluid and a shaft at the front of the cavity. Upon impact, the shaft is driven into the fluid, exerting a radial expanding force on the projectile. U.S. Pat. No. 3,429,263 to Snyder discloses a plastic bullet for dispensing paint onto the surface of a target, with the bullet carrying the paint in a tubular cavity. U.S. Pat. No. 6,675,718 to Parker teaches a method for making a fluid-filled projectile by first assembling a fluid-filled cylinder or capsule, and then inserting the cylinder into a hollow cavity of a bullet.
Despite the potential advantages of fluid-filled projectiles as taught by the prior art, they have had extremely limited to no commercial success. A primary reason for the lack of success is the fact that prior art fluid-filled projectiles exhibit unpredictable and uncontrolled expansion on a round-per-round basis. Predictable expansion is a primary factor when the military, law enforcement agencies, or hunters choose which bullet they are going to use. Accordingly, the military, law enforcement agencies, and hunters have not adopted fluid-filled bullets.
Thus, there is a need in the art for a fluid-filled projectile that expands in a predictable manner. Such a projectile would be useful in numerous military, law enforcement, and hunting applications.